M561 (Gamma Goat)

History

Given the active involvement of the French military in Southeast Asia, the U.S. military began work on a new logistics-focused cargo vehicle to accompany its new Ford-built M151 MUTT (dedicated to the post-war/Korean era Wiley Sjeep) M38 series). A formal contract offer was announced and received responses from multiple sources, although it finalized Ling-Temco-Vought (LTV) as lead designer. LTV introduced a six-wheel, 6x6 powered vehicle designed around a main four-wheel section (via a pivot) attached to a two-wheel trailer. Although the linkage separates the two sections, the front and rearmost axles work together, turning in opposite directions to achieve the desired turning radius.

The pilot vehicle was powered by an air-cooled engine, but was abandoned after evaluation in favor of a Detroit Diesel 3-53 3-cylinder, 103-horsepower, two-stroke diesel engine. Overall, the car weighs 7,000 pounds, has 15 inches of ground clearance, and can go 55 miles per hour on paved surfaces.

Additionally, the vehicle exhibits excellent off-road maneuverability and acquires an inherent (albeit limited) amphibious capability thanks to its articulated 6x6 drivetrain.

The "Gamma Goat" - named after Roger Gamount, the designer of the articulated joint, and the excellent climbing qualities of the ibex - entered the US Army stockpile in 1969, with deliveries ending in 1973 (according to the official name of "M561, 6x6, Tactical, 1-1/4 Ton Truck"). Over time, a medically focused transport variant, the M792, was also developed.

Production moved to CONsolidated Diesel Electric Company (CONDEC) in North Carolina.

The M561 proved itself to be an aircraft carrier, although the design was not without its problems. The diesel engine has no muffler, and its location behind the driver causes noise problems. Vehicles are so loud that hearing protection becomes standard for their drivers.

It also means the vehicle is proving to be tactically resilient near active battle lines - especially when used as a personnel carrier. When combined with fast-moving wheeled convoys, the system is typically slow, and its amphibious capabilities become a questionable featurethe Gamma Goat needs fairly calm water to traverse, with a top speed of just 2.5 mph (motion control only through the action of its spinning wheel).

Mechanics don't like hard-to-reach parts of the vehicle, which increase service time, and while the 6x6 machine excels off-road, turning to the 6x6 machine on stable, flat roads proves a challenge for the inexperienced.

The gamma goat produced 15,274 samples before the production run was complete. They remained in U.S. Army inventory for the remainder of the Vietnam War before eventually being abandoned with the arrival of cheaper commercial vehicles and the ubiquitous HUMVEE utility vehicle. During its life cycle, the Gamma Goat has transformed from its basic personnel/cargo carrier form into a specialized mortar, point gun, radar, ambulance and communications vehicle.

The M561 is only in service with the Mexican Army and Navy.

Specification

Basic

Roles

Dimensions

Performance

Performance

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Armor

Depends on the weapon carried.

Changes